This lecture discusses the basic concepts related to software design. Design is all about the creativity; design is the representation/model/development of the system or software to achieve goals within constraints. Goals may be the stakeholder requirements, business needs, and technical considerations. Constraints are often related to time, cost, quality, and technology. Software design includes architecture, components, data structures, andinterfaces. | Chapter 17 – Distributed software engineering Chapter 17 Distributed software engineering 1 20/11/2014 Topics covered Distributed systems Client–server computing Architectural patterns for distributed systems Software as a service Chapter 17 Distributed software engineering 2 20/11/2014 Distributed systems Virtually all large computer-based systems are now distributed systems. “ a collection of independent computers that appears to the user as a single coherent system.” Information processing is distributed over several computers rather than confined to a single machine. Distributed software engineering is therefore very important for enterprise computing systems. 20/11/2014 Chapter 17 Distributed software engineering 3 Distributed system characteristics Resource sharing Sharing of hardware and software resources. Openness Use of equipment and software from different vendors. Concurrency Concurrent processing to enhance performance. Scalability Increased throughput by adding new resources. Fault tolerance The ability to continue in operation after a fault has occurred. 20/11/2014 Chapter 17 Distributed software engineering 4 Distributed systems Chapter 17 Distributed software engineering 5 20/11/2014 Distributed systems issues Distributed systems are more complex than systems that run on a single processor. Complexity arises because different parts of the system are independently managed as is the network. There is no single authority in charge of the system so top-down control is impossible. Chapter 17 Distributed software engineering 6 20/11/2014 Design issues Transparency To what extent should the distributed system appear to the user as a single system? Openness Should a system be designed using standard protocols that support interoperability? Scalability How can the system be constructed so that it is scaleable? Security How can usable security policies be defined and implemented? Quality of service How should the quality of service be specified. Failure . | Chapter 17 – Distributed software engineering Chapter 17 Distributed software engineering 1 20/11/2014 Topics covered Distributed systems Client–server computing Architectural patterns for distributed systems Software as a service Chapter 17 Distributed software engineering 2 20/11/2014 Distributed systems Virtually all large computer-based systems are now distributed systems. “ a collection of independent computers that appears to the user as a single coherent system.” Information processing is distributed over several computers rather than confined to a single machine. Distributed software engineering is therefore very important for enterprise computing systems. 20/11/2014 Chapter 17 Distributed software engineering 3 Distributed system characteristics Resource sharing Sharing of hardware and software resources. Openness Use of equipment and software from different vendors. Concurrency Concurrent processing to enhance performance. Scalability Increased throughput by adding new .
